Access to safe drinking water has been described by the World Health Organization as a basic human right that is essential to health. While there are many sources from which fresh water could be obtained, such as groundwater, upland lakes and reservoirs, and rivers, such water may not be suitable for drinking due to presence of various microorganisms in the water. The microorganism contamination can pose immediate health risks, such as when the water is contaminated with pathogenic strains of E. Coli bacteria, cholera causing Vibrio cholera, viruses, and protozoan parasites, such as Giardia lamblia. Making the water suitable for drinking requires disinfection, preferably to the point of sterilization. As the size of the population requiring the drinking water, and consequently the volume of drinking water needed, grows, the challenge of purifying the water to a sufficient extent to make the water suitable for drinking similarly becomes larger.
Several techniques are currently in use for disinfection of water, but these techniques have significant drawbacks. For example, addition of chemicals, such as chlorine-containing compounds, have only limited effectiveness against pathogenic protozoa such as Giardia lamblia. Likewise, while disinfecting water with ultraviolet light is effective in low turbidity water, the effectiveness decreases as the turbidity increases.
Disinfection using ozone, which can act as a strong oxidizing agent that is toxic to most water-borne microorganisms, provides an effective alternative to chemical-based and ultraviolet-light based water sterilization. Ozone is created by passing oxygen through an ultraviolet light or a cold electrical discharge and is added to the water by bubble contact.
A concentration of 1-3 ppm within the water being purified is generally required for the ozone to be an effective disinfecting agent, with a higher concentration being potentially damaging to the pipes carrying the ozonated water. Introducing ozone into the water in that concentration may be a challenge that requires significant resources and that current techniques are not efficient at handling, especially in industrial settings, such as when the ozonation has to be performed at a water treatment plan responsible for providing drinking water to a large city. For example, a bubble diffuser is a device for dissolving ozone into water in which a porous object is used to break ozone gas into small bubbles at the bottom of a water basin with the bubbles slowly rising to the top of the basin and partially dissolving in the water. However, the efficiency with which a bubble diffuser dissolves ozone tends not to exceed 75%, with the at least 25% inefficiency making the purification unnecessarily expensive and wasteful, especially as higher volumes of water are processed. While the efficiency may be improved by increasing the depth of the water basin, such an increase may not be commercially viable nor technically practicable in a industrial application.
Accordingly, there is a need for a way to perform efficient water purification using ozone that is also scalable for industrial-scale water disinfection.